IME Theses and Dissertations
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Begun, Syeda Sayeedunissa (Wichita State University, May , 2011)[more][less]
Abstract: Surveys are an effective way of collecting customer feedback. Open-ended survey questions capture important dimensions of the respondent’s experience. The purpose of this study was to compare the critical incident technique (CIT) and the concept mapping approach (CMA) with respect to their ability to identify major customer requirements and the time required to complete each analysis. A case study was performed to identify students’ requirements of in class presentation. Answers to the open ended questions were analyzed using the two techniques. Results of this case study indicated that the CIT appears to be more appropriate for scenarios where continual participation from members of the survey population is not feasible. Otherwise, the CMA would be chosen for analyzing written comments. Description: Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering. URI: http://hdl.handle.net/10057/3980 Files in this item: 1
t11045_Sayeedunissa Begum.pdf (709.5Kb) -
Venkataraju, Ram Prasaad (Wichita State University, December , 2010)[more][less]
Abstract: Buffers are inventory held in between machines to avoid stockout of parts. When a company has large buffer quantities between machines the inventory holding cost increases. Reducing the amount in a buffer increases the chance of stockout and hence will have a direct impact on the throughput of the line. Hence there is a need to maximize the throughput of the production line for a minimum quantity of buffers carried between machines. In large volume manufacturing, homogeneous unreliable serial parallel production lines are typical. For this line, a method is developed to identify the buffer allocation that maximizes the throughput of the line with a constraint on the maximum buffer size that can be held in the line. The developed method is implemented in case studies to identify buffer allocation that maximizes throughput. Description: Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering. URI: http://hdl.handle.net/10057/3755 Files in this item: 1
t10126_Venkataraju.pdf (1.358Mb) -
Swaminathan, Palanivel (Wichita State University, December , 2010)[more][less]
Abstract: Segmented chips that arise as a result of formation of adiabatic shear bands are common in high-speed machining of harder alloys. Analytical models describing the mechanics of segmented chip formation have been developed, and these models do not assume or require failure in the material. Most of the finite element (FE) studies of segmented chip formation in the literature always include failure in the material. This thesis presents a numerical study of the occurrence of adiabatic shear banding without material failure. Here, the mechanical properties of hardened 4340 steel was used as a base line, and Johnson and Cook material model for this material were modified to make the material more prone to shear banding. Simulations were performed in two different commercial FE packages: ABAQUS/Explicit and LS-DYNA. The arbitrary Lagrangian-Eulerian (ALE) approach in ABAQUS/Explicit showed shear banding when mass scaling factor was 100. The same simulation did not show shear banding once the mass scaling was removed. Also, the simulations with accelerated thermal softening kept crashing; likely due to the onset of shear banding causing too much mesh distortion. Since steady state was not achieved with any of these simulations, it is hard to say exactly how the intensity of shear banding changes with material properties. Finite element studies in the recent literature, where researchers have shown shear banding through strain softening without material failure using the updated Lagrangian approach, were repeated with ALE in ABAQUS. With the reduction in the parameter controlling the curvature based mesh refinement, shear banding has been successfully simulated in ABAQUS. ALE approach in ABAQUS did not produce the same chip geometry shown in literature because the simulations failed since the mesh was not able to reform to vii a large extent and produce concave shapes as we see in serrated chips. Mass scaling with a factor of 100 did not affect the result. It should be noted that the strain seems to diffuse with the increase in the element size. So, smaller elements are needed to better capture the strains along the PSZ. Lagrangian analysis with a parting-layer approach in LS-DYNA showed shear banding for different plastic properties of the material and no shear banding for others. Observations of the effect of different material and mesh parameters on the shear banding intensity have been made from the simulations and future research are proposed. Description: Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering. URI: http://hdl.handle.net/10057/3750 Files in this item: 1
t10121_Swaminathan.pdf (2.603Mb) -
Solaimuthu Pachaimuthu, Sathya Madhan (Wichita State University, December , 2010)[more][less]
Abstract: In general, manufacturing systems could be classified into machine intensive manufacturing and labor intensive manufacturing. From the previous studies, we can infer that worker allocation plays an important role in determining efficiency of a labor intensive manufacturing system. Most of the research works in the previous literature is performed in a deterministic bed. But from the time study data that was obtained from a local aircraft company shows a high degree of variability in worker processing times. Thus this research presents a worker allocation approach which also considers the uncertainty in worker processing times into account. Risk based worker allocation approach is developed for three different scenarios. First scenario is the single task per station balanced production line scenario, where workers are allocated to processes by minimizing the overall risk of delay due to workers. In the second scenario, in addition to worker allocation by minimizing the overall risk, multiple workers are allocated to processes to make the flow of products uniform in a single task per station unbalanced production line. Prior to implementing the final approach, a method for line balancing when variability is involved is studied and compared to the ranked positional-weight method. The final scenario developed is a simultaneous approach to balance and allocate workers in a multiple task per station production line. Case studies were simulated using QUEST software and the result indicates that risk based allocation has increased throughput and efficiency compared to deterministic worker allocation. Description: Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering. URI: http://hdl.handle.net/10057/3744 Files in this item: 1
t10115_Solaimuthu Pachaimuthu.pdf (740.5Kb) -
Pandiripalli, Bhavani (Wichita State University, December , 2010)[more][less]
Abstract: Gage Repeatability & Reproducibility (GRR) Studies have become critical in process improvement projects in the manufacturing sectors. There are various methods to conduct GRR study. However, the most widely used is the Automotive Industry Action Group (AIAG) method, which was standardized after the recognition of the importance of measurement systems. In this study, AIAG method and Wheeler’s method are compared, with specific interest in the proportions of the estimates of variation. An experimental study was designed, with factors being the operators and parts. The spectrum analyzer – Quattro, was tested for its adequacy of measurement and to understand the variability in the measurement system. In this research, vibration-impact testing was performed on Stereolithography (SL) parts and the measured feature was the natural frequency. The data was analyzed following the AIAG method and that proposed by Wheeler. From the results obtained, the Repeatability and Reproducibility were over estimated by AIAG method in comparison to Wheeler’s. The Wheeler’s method gave a better understanding of the sources of variation. Due to which, the measurement system capability could be judged without bias. Also, Wheeler’s method helps in making right decisions about the measurement system. Therefore, Wheeler’s method is strongly recommended over the AIAG. Description: Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering. URI: http://hdl.handle.net/10057/3736 Files in this item: 1
t10107_Pandiripalli.pdf (3.655Mb)
